Making a cumulative sum column

[cool-RR]

I want to make a column that's a cumulative sum of another column. I'm assuming I should make a "derivative column" but the docs don't make it clear how to access items of other columns that are on preceding rows. Is this possible without creating my own script?

[cool-RR]

I made my own script, but if there's a native way to do such things I'll be happy to know. My script:

@Sheet.api
def addcol_cumsum(sheet: Sheet, column: Column) -> None:
    """Add column with cumulative sum of values in current column."""
    getter = lambda c, row: sum(c.sourceCol.getValues(sheet.rows[:sheet.rows.index(row)+1]))
    cumsum_column = Column(f'{column.name}_cumsum', type=column.type, getter=getter)
    cumsum_column.sourceCol = column
    sheet.addColumnAtCursor(cumsum_column)

Sheet.addCommand('Ins =', 'addcol-cumsum', 'addcol_cumsum(cursorCol)', 
                'add column with cumulative sum of current column')